1. Technical Field
The present invention is concerned with a semiconductor structure that is especially useful in optical devices such as light emitting diodes (LED), lasers and light amplifiers. In particular, the present invention is concerned with a semiconductor structure that includes a rare-earth dopant.
2. Background Art
Optoelectronic devices convert optical signals into electrical signals and, conversely, convert electrical signals to optical signals in the form of photons of light emitted. In recent years, to a large extent optoelectronic devices depend on microelectronic devices. To a greater extent, optoelectronic components employ so-called III/V semiconductor elements for lasers, light emitting diodes and the like. Group III-V is semiconductors have as one element at least one member of the group IIIA of the periodic table (e.g. Al, Ga, In, Tl) and as a second element at least one member of the group VA of the periodic table (e.g. P, As, Sb and Bi). To a lesser extent, silicon-based devices have been used for such purposes. In view of the difficulties encountered in obtaining Si-based lasers, LEDs or amplifiers that operate at the commercially interesting wavelengths of about 1.3 to 2.5 xcexcm. Nevertheless, it would be desirable to have Si-based optoelectro devices since the availability of these devices would greatly ease the difficulty of integrating optical and electronic functions on a single semiconductor chip. Moreover, the high thermal conductivity of silicon provides for certain operational advantages.
More recently, it has been found that doping of silicon with a rare-earth element such as erbium results in emitting light at wavelengths of about 1.5 xcexcm under photo and electrical stimulation. Emission of light at this wavelength, which occurs via intra-4f level transitions of excited rare-earth element atoms, is desirable since it coincides with an absorption minimum of silica-based fibers.
Furthermore, electroluminescence has been demonstrated in both forward- and reverse-biased p-n junctions formed in erbium-oxygen-doped silicon as discussed in Stimmer et al, Applied Phyics Letters, Vol. 68, No. 23, June 1996, p. 3290. Under reverse-bias, the rare-earth atoms are excited by an Auger mechanism or impact ionization process. On the other hand, under forward-bias, the rare-earth atoms are excited by energy transferred from an electron-hole recombination event mediated by the interaction of the rare-earth atom with the silicon electronic structure. Use of such devices has been restricted since the electroluminescence is limited by low current densities in reverse-bias and by a strong (inverse) temperature dependence due to competing recombination mechanism in forward-bias. It would therefore be desirable to overcome these problems existent in the prior art.
The present invention provides a solution to the above-discussed problems. In particular, the present invention provides for a source of carriers to the device instead of relying upon the leakage current that is caused by impact ionization. More particularly, the present invention is concerned with a bipolar structure that comprises a p-n junction in a semiconductor having a first p-type region and a first n-type region. A region is located in the vicinity of the p-n junction that is doped with a rare-earth element. In addition, charge carrier means for exciting atoms of the rare-earth element is provided.
The present invention is also concerned with the method of producing such a device. In particular, the method of the present invention comprises providing a bipolar junction transistor; doping a region in a collector of the transistor with a rare-earth element; and biasing the transistor to generate light emission from the rare-earth element doped region.
Still other objects and advantages of the present invention will become readily apparent by those skilled in the art from the following detailed description, wherein it is shown and described only the preferred embodiments of the invention, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not as restrictive.